Al_xGa_yIn_1-x-yAs/InP-based quantum well infrared photodetectors

In order to tune the wavelength of a lattice-matched quantum well infrared photodetector (QWIP) over the range 3-20 μm, new designs are demonstrated for the first time which utilise Al_xGa_yIn_1-x-yAs layers lattice-matched to InP and grown by gas-source molecular beam epitaxy. We demonstrate 8, 13, and 18-μm QWIPs using the lattice-matched n-doped (Al_xGa_1-x)_0.48In_0.52As /InP system. We also review QWIP structures of Ga_0.47In_0.53As/Al_0.48In_0.52As grown on InP substrate with peak photoresponse at 4 μm. Combining these two materials, we report the first multicolour detectors that combine lattice-matched quantum wells of Ga_0.47In_0.53As/ Al_0.48In_0.52As and Ga_0.47In_0.53As/InP. Utilising two contacts, a voltage tunable, lattice-matched, two colour QWIP with a peak wavelength of 8 μm at a bias of V = 5 V and a peak wavelength of 4 μm at V = 10 V is demonstrated. Using the measured noise data for Ga_0.47In_0.53As/InP detectors, we have calculated the thermal generation rate, bias-dependent gain, electron trapping probability, and electron diffusion length. The calculated thermal generation rate (∼7 × 10²² cm^-3s^-1) is similar to Al_xGa_1-xAs/GaAs QWIPs with similar peak wavelengths, but the gain is 50 times larger, indicating improved transport and carrier lifetime are obtained in the binary InP barriers.